EWI on 3 sides and pumped on front

Minier81

Hi all, another external wall insulation question. We want to get EWI as we have cavity block in all walls except front wall which is hollow with a brick front. Our plan was to do EWI on all four walls which we know is more expensive. We have a contractor telling us we are really wasting money doing this and just do the 3 walls in EWI and pump the front one. We want to do a good job and don'tmins paying for it but also don't want to be wasting money. Are we being silly with doing EWI on top of pumping the front wall? It gets expensive because doing this will invoice doing a new brick facade.

MightyMunster

3 houses in my estate have got EWI and none of them did it on the red brick front.

Calahonda52

is the house detached?

are you getting new windows?

why the new brick facade?

will the brick facade take to being pumped from behind? if its not structural, maybe not, also potential damp issues

the issue is thermal bridging and a difference in the thermal performance

Minier81

Its is detached, we are not getting new windows as we updated to triple glaze windows several years ago.

The new facade is because we are unsure if pumping alone will be a good enough job for the front wall. I though pumping was not great. Our plan is to pump front wall, place ewi on the exterior face and new facade on top of that. Alternative is to just pump and our redbrick stays as is.

listermint

The installer will say that because they don't like having to deal with brick slips fascades also the brick slips are back logged presently transport delays brexits.

Handier for him to pump.

For me it's simply not as good a job as wrapping all fascades. You will be left with thermal bridging points at the corners.

Biker1

If EWI is to be done on a cavity wall then the cavity should be pumped also to prevent thermal looping.

RandRuns

I would be worried that about interstitial condensation with the front wall.

Minier81

listermint wrote: »

The installer will say that because they don't like having to deal with brick slips fascades also the brick slips are back logged presently transport delays brexits.

Handier for him to pump.

For me it's simply not as good a job as wrapping all fascades. You will be left with thermal bridging points at the corners.

Thanks this was exactly what I am looking for advice on, we would rather do the full wrap around if its a better job.


Very interesting about the façades and brick slips and delays. He may have been trying to sway me from them for this reason. He also told me façades look awful after a few years, and get the brick slips if anything.

Minier81

RandRuns wrote: »

I would be worried that about interstitial condensation with the front wall.

This would be a worry if you only got it pumped? Or anyway?

Minier81

Biker1 wrote: »

If EWI is to be done on a cavity wall then the cavity should be pumped also to prevent thermal looping.

Thank you. Yes this is what we are looking at pumped and EWI on the front cavity wall.

RandRuns

Minier81 wrote: »

This would be a worry if you only got it pumped? Or anyway?

It happens where the dew point is anywhere further in than the external surface of the wall. I've found pumped walls prone to it anyway, But I'd be even more concerned where only one facade was pumped and the others EWI as I think the thermal difference could bring the dew point in further on the pumped wall.

whizbang

we have cavity block in all walls except front

Why does this not raise a very large red flag...?

Cavity should be treated as outside for all purposes re insulation. EWI on cavity block is like installing insulation on your garden walls, to keep your garden warm.
In the rare case that the cavity is fully sealed you may get an improvement, but its too much of a gamble.
Cavity blocks are designed to have airflow through the cavity.

Calahonda52

whizbang wrote: »

Why does this not raise a very large red flag...?

Cavity should be treated as outside for all purposes re insulation. EWI on cavity block is like installing insulation on your garden walls, to keep your garden warm.
In the rare case that the cavity is fully sealed you may get an improvement, but its too much of a gamble.
Cavity blocks are designed to have airflow through the cavity.

I don't follow the analogy.
Are most cavities not closed on top with a solid block to take the wall plate, which is why the ewi must go up beyond the soffit to meet the being insulation

whizbang

Most older houses are not closed on top of cavity.
While I dont have much knowledge about installations, I cant imagine many EWI installations wrapping over the top of the wall plate.

Calahonda52

whizbang wrote: »

Most older houses are not closed on top of cavity.
While I dont have much knowledge about installations, I cant imagine many EWI installations wrapping over the top of the wall plate.

Well thats the only way to do it properly, otherwise its like an insulation belly top, with a massive cold bridge all the way around

monseiur

Minier81 wrote: »

Hi all, another external wall insulation question. We want to get EWI as we have cavity block in all walls except front wall which is hollow with a brick front. Our plan was to do EWI on all four walls which we know is more expensive. We have a contractor telling us we are really wasting money doing this and just do the 3 walls in EWI and pump the front one. We want to do a good job and don'tmins paying for it but also don't want to be wasting money. Are we being silly with doing EWI on top of pumping the front wall? It gets expensive because doing this will invoice doing a new brick facade.

If you want bang for your buck go for internal insulation (dry lining) - 62.5mm insulated slab should do and ensure that your attic has at least 300mm insulation. It's fairly labour intensive around windows etc. but worth it in the long run. It should work out cheaper than EWI, but obviously a lot messier.
If it's a two story house start upstairs and work your way down.
EWI on hollow block wall is a money down the drain and don't let anyone convince you otherwise - once the heat penetrates the wall into the cavities of the block 75% is gone, and as they say in all the best ads. when it's gone it's gone.

BryanF

monseiur wrote: »

.
EWI on hollow block wall is a money down the drain and don't let anyone convince you otherwise - once the heat penetrates the wall into the cavities of the block 75% is gone, and as they say in all the best ads. when it's gone it's gone.

That’s totally incorrect.

As long as the EWI extends to the footings and is wrapped over capped cavity block at the eaves there is no issue.

EWI is a far more complete, continuous envelope solution In comparison to Piece meal Room by room drylining, with thermal gaps at every wall floor and ceiling.

Edit: OP this topic has been covered to death in this forum going back ten or so years, so many of the regular archs/eng’s who post here, just haven’t bothered to show up in this thread. Suggest you read around the forum, look for posts by sydthebeat, Sinnerboy, et al

tobeme2020

What about ewi on 3 sides and 100mm internal insulation on the front wall and the cavity pumped. Extend the artic insulation over the cavity bloser block. This should do OK. I know someone who did this because they had stone on the front of there house and no issues with thermal bridging or cold spots.